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Notice of GPS week number rollover on GPS Navigator / Sensor

To All Customers:

We greatly appreciate your use of our products.

This is to inform you of the “GPS week number rollover” problem and how it affects our GPS Navigator / Sensor.

The GPS system calculates time by counting the number of weeks up to a maximum of 1,023 weeks. After week 1,023, the week number count is reset to zero. This is called “GPS week number rollover”.

The GPS week number rollover occurs every 1,024 weeks - about once every 19.6 years. Therefore, when 19.6 years has passed from the reference date in the systems, the clock time incorporated in GPS sensors and navigators will be reset, causing as a result errors in display or output of date, or unstable occurrence in positioning operation.

When GPS week number rollover occurs, our GPS Navigator / Sensor may cause the following problems:

  1. Date displayed dates back to 19.6 years ago.
  2. All dated data output by equipment date back to 19.6 years ago.
  3. Due to this inaccurate date, positioning operation may temporarily become unstable or be interrupted.

When this rollover has occurred, please switch on the equipment twice to recover the normal positioning operation. After recovery of the operation, the date will remain as it is in 19.6 years ago, but time and positioning operation will function normally.

We regret any inconvenience this may cause you, but appreciate your kind understanding in this matter.

Sincerely yours,

Affected GPS Navigator / Sensor and Countermeasures

  • When the dated data displayed on equipment and the dated data output from equipment are not used, there would be no need to take countermeasures. When data is continued to be used, either one of the following countermeasures shall be taken:
    1. Upgrade of software version.
    2. Replacement of equipment (When equipment can not be dealt with by upgrade of software version).

Please refer to the tables below for countermeasures for each type of equipment.

It is possible to postpone the occurrence of rollover to the year of 2028 by upgrading of software, but it may not be possible to upgrade software, even if charge is paid, as the needed ROM software may not be available on all models. In such cases, replacement of equipment will be provided with charge. Please contact our distributors / dealers where you have purchased or our marine sales department for details on the equipment subject “upgrading of software version”. We appreciate your kind understanding that the cost shall be born by you for either case of the countermeasure above mentioned.

  • In the tables below, only equipment expected to have this rollover in years of 2010, 2012 and 2013 are listed. Equipment not listed can be expected to have this rollover in the year of 2018 or later and therefore they are not listed at this time.
  • Even on the same equipment models, this phenomenon may occur on a different date, due to its software number and version number. The tables below list the earliest possible date of occurrences.

Table 1 - GPS Sensors

Date of
rollover occurrence
Model Name Countermeasures
August 15, 2010 GPS-4A Unit replacement is necessary
August 15, 2010
GPS-5 Unit replacement is necessary
February 5, 2012 GPS-4Amk2 Unit replacement is necessary
February 5, 2012 GPS-6 Unit replacement is necessary
January 20, 2013
GPS-10 Unit replacement is necessary
January 20, 2013 GPS-10A Serial No.1005937 and before:
Unit replacement is necessary
Serial No 1005938 and after:
Upgrading of software
January 20, 2013 KBG-1 Upgrading of software
January 20, 2013 KBG-2/DGPS-11 Upgrading of software

Table 2 - GPS Navigators

Date of
rollover occurrence
Model Name Countermeasures
August 15, 2010 KGP-95/GPS-7 Unit replacement is necessary
August 15, 2010
KGP-97/GPS-8 Unit replacement is necessary
August 15, 2010 KGP-910/910A
GPS-77P
Unit replacement is necessary
August 15, 2010 KGP-911/GPS-88P Unit replacement is necessary
August 15, 2010 KGP-930 Unit replacement is necessary
February 5, 2012 KGP-98/98D
GPS-9/9D
Unit replacement is necessary
February 5, 2012 KGP-931 Unit replacement is necessary
January 20, 2013 KGP-9/HG-7 Unit replacement is necessary
January 20, 2013 KGP-912/GPS-99P Serial No.91208112 and before:
Unit replacement is necessary
Serial No 91208113 and after: Upgrading of software
January 20, 2013 KGP-913/913D
GPS-90/90D
Upgrading of software
January 20, 2013 KGP-931D Serial No.93101280 and before:
Unit replacement is necessary
Serial No.93101281 and after: Upgrading of software

Table 3 - Chart Plotters

Date of
rollover occurrence
Model Name Countermeasures
August 15, 2010 KGF-960 Unit replacement is necessary
August 15, 2010 GTD-07 Switch on the power supply twice
August 15, 2010 GTD-2000 Unit replacement is necessary
August 15, 2010 GTD-2020 Switch on the power supply twice
August 15, 2010 GTD-210 Unit replacement is necessary
August 15, 2010 GTD-2200/2200X Switch on the power supply twice
August 15, 2010 GTD-2210 Switch on the power supply twice
August 15, 2010 GTD-2400 Switch on the power supply twice
August 15, 2010 GTD-2410 Switch on the power supply twice
February 5, 2012 GTD-1100 Unit replacement is necessary
February 5, 2012 GTD-2010 Switch on the power supply twice
January 20, 2013 GTD-1200 Unit replacement is necessary

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